The invention relates to methods of dialing and particularly to automated methods of dialing in mobile radio telephone systems.
Known mobile radio telephone systems utilize a number of different signalling formats to communicate from one portion of the telecommunication system to another. The problems caused by differing signalling formats are particularly acute when a mobile radio telephone user desires to use a long distance subscriber system which is operated by an operator different from the operator of the mobile telephone system. Typically, in utilizing such long distance subscriber systems, a mobile radio telephone user must first dial a telephone number to establish a telephone call between the mobile unit and a local telephone number assigned to the long distance subscriber system. Once the user has gained access to the long distance subscriber system, the user is presented with a supervisory tone from the long distance subscriber to inform the user that the system is available and ready for operation. Often the user is required to key in a five-digit billing code followed by the seven to ten-digit telephone number of the remote location with which communication is desired.
Thus the dialing from a mobile telephone of a long distance telephone number through a long distance subscriber system may entail the dialing of three or more sets of numbers. Since many mobile telephones are installed in automobiles that are used while the telephone operator is driving the automobile, it is often difficult for the telphone user to divert his attention from the traffic in order to dial the many digits required. Additionally, the sets of numbers must stop and be dialed after receiving an acknowledgement signal from the system being dialed that the system is ready for dialing. For example, when the mobile telephone user indicates to the system that he desires to place a call, it may be a matter of thirty or more seconds before the mobile equipment has completed the initial channel assignment and hand-shaking routines with the base station and is ready to dial the desired local number. Similarly, it may take quite a few seconds for the call to be answered by the long distance subscriber system and there may be even a further wait associated with the validation and acceptance of the accounting code before the long distance subscriber system presents the supervisory tone to permit dialing of the ultimate telephone number. Given the unpredictability of the length of time associated with each one of these delays, it is usually not possible for the driver of an automobile to plan to divert his attention from his driving tasks at the appropriate times to continue the dialing sequence. Failure to timely resume the dialing procedures generally requires that the entire sequence begin anew.
The difficulties associated with dialing a long distance subscriber system through a mobile telephone unit are further complicated by the fact that often the initial call is placed using a signalling technique such as frequency shift keying to indicate the local telephone number and the long distance subscriber system responds to dual tone multifrequency ("DTMF") format signalling. While it is possible to equip the mobile telephone system with a manual switch by which the operator can command the mobile telephone to switch formats from FSK to DTMF, such a switch adds another level of complexity to the task of manually dialing the mobile telephone as it is another step which must be accomplished by the mobile telephone operator.
In land based telephone systems and in some mobile telephone systems, it is known to use repertory dialing to reduce the burden of dialing frequently called telephone numbers. In such systems, an entire telephone dialing sequence comprising a plurality of individual dialing commands or digits is stored in a memory device. Often, a plurality of such telephone dialing sequences are stored in the device and each dialing sequence is referenced by an index. To dial one of the dialing sequences, a user first indicates to the telephone instrument that he desires to use the repertory dialing capability and then indicates the identification of the index associated with the repertory dialing sequence which the user desires. Upon receipt of the repertory dialing request, the telephone instrument automatically retrieves the dialing sequence from the memory device and transmits the dialing signals appropriate to each digit of the dialing sequence.
In dialing using a long distance subscriber network, it is advantageous to be able to store and subsequently recall at least three different repertory dialing sequences: the telephone number of the local access to the long distance subscriber system; the billing account number of the telephone user; and the long distance number of the party desired to be called. However, many of the known repertory dialing telephone instruments do not permit repertory dialing commands to be concatenated, i.e., all the dialing commands to be entered at once in the order desired. Moreover, since the user must frequently wait for the receipt of a supervisory tone between the dialing of the local access number, the dialing of the account billing number, and the dialing of the number of the called party, simply concatenating the three desired numbers in a repertory dialing sequence will not accomplish the required dialing, since the required pauses may be ignored.
In using a memory device to store the dialing sequences, many known telephone instruments reserve a predetermined number of memory locations for each dialing sequence. For example, a memory device capable of storing 200 individual digits may be partitioned into ten storage areas or registers, each register being associated with a dialing sequence. In such telephone instruments, the number of storage locations assigned to each register and reserved for each dialing sequence is often gauged at the size of the longest dialing sequence customarily used. For example, to dial from a telephone in the United States to certain European countries, the dialing of up to twenty digits is frequently required. Thus, many known repertory dialing systems reserve twenty digits for storage of each repertory dialing sequence. Since most local or even U.S. long distance telephone numbers require the dialing of only seven or ten digits, the reservation of twenty digits for the storage of repertory dialing sequences may result in the nonuse of a significant number of memory storage locations.
It is therefore an object of the present invention to provide a mobile telephone instrument which obviates one or more of the problems of prior art instruments and to provide a novel method and apparatus for dialing mobile telephones.
It is another object of the present invention to provide a novel method and apparatus for storage of repertory dialing sequences.
It is still another object of the present invention to provide a novel method of dialing mobile radio telephones in which the dialing sequences are performed automatically in a plurality of signalling formats.
It is a further object of the present invention to provide a novel method and apparatus for determining the presence of a supervisory tone on a mobile telephone receiver.
It is still a further object of the present invention to provide a novel method and apparatus to automatically dial a long distance subscriber service or the like without the need to manually change signalling formats and without the need to manually restart the dialing sequence upon receipt of a supervisory tone.
It is yet another object of the present invention to provide a novel method and apparatus for concatenating multiple repertory dialing sequences in a mobile telephone instrument.
These and other objects and advantages of the present invention will best be understood by reference to the following specification taken in connection with the accompanying drawings.